1. Field of the Invention
The present invention relates to thermocouple probes and more particularly to a fast response hand-held surface probe.
2. Description of the Prior Art
Heretofore thermocouple surface probes having acceptable response times and accuracies have been difficult to manufacture and as a result have been too expensive for many applications. Examples of such devices may be found in U.S. Pat. Nos. 3,395,050; 3,573,995; and 4,279,154. To assure good contact with the surface, the temperature of which is to be measured, spring members were used to urge the thermocouple junction against the surface. At times these spring members became quite elaborate since the mass of the spring could not be near the junction or it would act as a heat sink resulting in erroneous temperature readings. In most cases the thermocouple junction was formed by butt welding the ends of two strips of thermocouple metals. The junction was usually formed on a bias necessitating machining of the ends prior to welding and subsequent dressing of the junction to remove burrs or bumps resulting from the welding operation.
In an effort to reduce the cost of the welding and machining operations, attempts were made to form the junction by overlapping the metals and spot welding them together. Examples of these types of devices are shown in U.S. Pat. Nos. 2,282,441 and 3,283,580. The difficulty associated with this type of structure was lack of good contact with the surface. The overlapped metal reduced the metal area in contact with the surface and the structure provided insufficient contact pressure.
U.S. Pat. No. 3,099,575 shows a thermocouple probe wherein film ribbons of thermocouple metals are deposited on a refractory rod with the junction formed at the crossing of the film ribbons. The film is deposited directly on the rod so that the rod acts as a heat sink. Such a structure is not appropriate for a hand-held surface probe and must be used in permanent locations since response time is slow.